Apparatus for controlling reaction temperatures

ABSTRACT

A reactor arrangement and process for indirectly contacting a reactant stream with a heat exchange stream uses an arrangement of heat exchange plates to control temperature conditions by varying the heat transfer factor in different portions of a continuous channel defined by the heat exchange plates. The reactor arrangement and process of this invention may be used to operate a reactor under isothermal or other controlled temperature conditions. The variation in the heat transfer factor within a single heat exchange section is highly useful in maintaining a desired temperature profile in an arrangement having a cross-flow of heat exchange medium relative to reactants. The corrugations arrangement eliminates or minimizes the typical step-wise approach to isothermal conditions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional application of prior application Ser.No. 08/365,622, filed Dec. 28, 1994, now issued as U.S. Pat. No.5,600,052, which is a continuation-in-part of prior application Ser. No.08/236,072, filed May 2, 1994, now issued as U.S. Pat. No. 5,525,311,and the contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to chemical reactors for the conversion of areaction fluid while indirectly exchanging heat with a heat exchangefluid.

BACKGROUND OF THE INVENTION

In many industries, like the petrochemical and chemical industries forinstance, the processes employ reactors in which chemical reactions areeffected in the components of one or more reaction fluids under giventemperature and pressure conditions. Many of these reactions generate orabsorb heat, to varying degrees, and are, therefore, exothermic orendothermic. The heating or chilling effects associated with exothermicor endothermic reactions can positively or negatively affect theoperation of the reaction zone. The negative effects can include amongother things: poor product production, deactivation of the catalyst,production of unwanted by-products and, in extreme cases, damage to thereaction vessel and associated piping. More typically, the undesiredeffects associated with temperature changes will reduce the selectivityor yield of products from the reaction zone.

One solution for controlling the changes in temperature associated withthe heats of various reactions has been to operate several adiabaticreaction zones with intermediate heating or cooling between thedifferent reaction zones. In each adiabatic reaction stage, all of theheat liberated or absorbed during the reaction is transmitted directlyto the reactive fluid and the reactor internals. The degree of heatrelease and the tolerance for temperature change determines the totalnumber of adiabatic reactor zones required in such arrangements. Eachzone or adiabatic stage of reaction adds significantly to the overallcost of such a process due to the equipment expense of adding piping andheaters or coolers for intermediate stages of heat transfer to areactant that passes through the reaction zones. Therefore the number ofadiabatic steps is limited and such systems offer at best a stepwiseapproach to isothermal or other controlled temperature conditions.Moreover, the breaking up of a reaction zone into a series of reactorswith intermediate heating or cooling of reactants, especially interfereswith reactor arrangements that have continual addition and withdrawal ofcatalyst from the reaction zone.

Other solutions to the problem of temperature control under theinfluence of different heats of reaction have employed direct orindirect heating or cooling within the reaction zone. Direct heating orcooling utilizes a compensating reaction having a directionallydifferent heat requirement that occurs simultaneously with the principalreaction. The counter balancing reaction offsets heat release or heatadsorption from the principal reaction. One of the simplest forms ofsuch an arrangement is an endothermic process that uses oxidation ofhydrogen to heat reactants in an endothermic reaction.

Another solution has been the indirect heating of reactants and/orcatalysts within a reaction zone with a heating or cooling medium. Themost well known catalytic reactors of this type are tubular arrangementsthat have fixed or moving bed catalysts. The geometry of tubularreactors poses layout constraints that require large reactors or limitthroughput.

Indirect heat exchange has also been accomplished using thin plates todefine channels that alternately retain catalyst and reactants between aheat transfer fluid for indirectly heating or cooling the reactants andcatalysts. Heat exchange plates in these indirect heat exchange reactorscan be flat or curved and may have surface variations such ascorrugations to increase heat transfer between the heat transfer fluidsand the reactants and catalysts. Although the thin heat transfer platescan, to some extent, compensate for the changes in temperature inducedby the heat of reaction, the indirect heat transfer arrangements are notable to offer the complete temperature control that would benefit manyprocesses by maintaining a desired temperature profile through areaction zone.

Many hydrocarbon conversion processes will operate more advantageouslyby maintaining a temperature profile that differs from that created bythe heat of reaction. In many reactions, the most beneficial temperatureprofile will be obtained by substantially isothermal conditions. In somecases, a temperature profile directionally opposite to the temperaturechanges associated with the heat of reaction will provide the mostbeneficial conditions. An example of such a case is in dehydrogenationreactions wherein the selectivity and conversion of the endothermicprocess is improved by having a rising temperature profile, or reversetemperature gradient through the reaction zone.

A reverse temperature gradient for the purposes of this specificationrefers to a condition where the change in temperature through a reactionzone is opposite to that driven by the heat input from the reaction. Inan endothermic reaction, a reverse temperature gradient would mean thatthe average temperature of the reactants towards the outlet end of thereaction zone have a higher value than the average temperature of thereactants at the inlet end of the reaction zone. In an opposite manner,a reverse temperature gradient in an exothermic reaction refers to acondition wherein reactants towards the inlet end of the reactor have ahigher average temperature than the reactants as they pass toward theoutlet end of the reaction section.

It is an object of this invention to provide a reactor that offersgreater temperature control of reactants by the indirect heating orcooling of a reaction stream by a heat exchange fluid within a reactionzone.

It is a further object of this invention to provide a process andapparatus used for indirect heat exchange of a reactant stream with aheat exchange stream for controlling the temperature profile through thereaction zone.

Another object of this invention is to provide a process that usesindirect heat exchange with a heat exchange fluid to maintainsubstantially isothermal conditions or a reverse temperature gradientthrough a reactor.

It is a yet further object of this invention to provide a reactorarrangement and process that facilitates the continuous transfer ofcatalyst through a reaction zone that indirectly contacts a reactantstream with a heat exchange fluid.

BRIEF SUMMARY OF THE INVENTION

This invention is a chemical reactor and a process for using a chemicalreactor that employs an arrangement of heat exchange plates within thereactor that will maintain reactor temperatures within a desired rangeduring the reaction. The invention uses a variable heat transfer factoralong the length of a plate to control the amount of heat that isindirectly transferred to a reaction fluid over the length of the heatexchange plate. Varying the heat transfer factor will increase heattransfer to offset the effects of temperature changes in the heatexchange fluid when attempting to maintain a desired temperature profilefor a reactant stream. In the case of an endothermic reactiontemperature reduction in the heating medium may be offset by with acorresponding increase in the heat transfer factor to maintain a desiredtemperature of the reactants. Similarly for an exothermic reactionincreases in the temperature of a cooling fluid may be compensated forwith an increase in the heat transfer factor to maintain cooling of thereactants to a desired level. In this manner desired temperatureprofiles are maintained over a continuous reaction section without theintermediate addition or withdrawal of heat exchange fluid.

The heat transfer factor may be varied in any manner that will providecontinuous flow channels for the reactants and the heat exchange fluid.One manner of varying the heat transfer factor uses a plate havingpunched tabs and is shown in U.S. Pat. No. 5,538,700, the contents ofwhich are hereby incorporated by reference. In a preferred form of thisinvention the plates forming the reactant and heat exchange channelswill have corrugations formed over the length of the plate for improvingheat transfer across the plates. The heat transfer factor may becontrolled by varying the geometry of the corrugations over differentportions of the plates. Another parameter that can be controlled inaccordance with this invention to affect the heat transfer factor is avariation in the number of channels, also expressed the spacing betweenheat exchange plates, over the length of a heat exchange zone in areactor. By varying any of these plate parameters, applicants havediscovered that a variety of temperature profiles includingsubstantially isothermal or even reverse temperature gradients can beachieved in a reaction zone.

This invention will permit desired control of temperatures through areaction zone. Preferably this invention will maintain the desired inletand outlet temperatures within 10° F. and more preferably within 5° F.of desired temperature difference. Where isothermal conditions aredesired the inlet and outlet temperature are equal, such that onerequirement of the substantially isothermal conditions described in thisinvention is that the mean inlet and outlet temperature vary by no morethan 10° F. and preferably by no more than 5° F.

A process and catalyst reactor arrangement that uses this invention mayuse single or multiple reaction zones within a reactor vessel. Theadvantage of this invention is that the reactor vessel can provide thedesired temperature gradient without intermediate withdrawal andrecycling of reactants or heat exchange medium between the inlet andoutlet of the reactor. Multiple reaction zones within the reactor vesselcan be used to accommodate variations in the heat transfer factor suchas changes in the depth or pitch angle of the corrugations in the heatexchange plates or changes in the number of heat exchange plates thatdefine the flow channels of the invention.

Accordingly, in an apparatus embodiment, this invention is a reactor forcontrolling temperature profiles in a reaction zone. The reactor has aplurality of spaced apart plates with each plate having an extendedlength and defining a boundary of a heat exchange flow channel on oneside of the plate and a boundary of a reaction flow channel on anopposite side of the plate. Each plate defines a first heat transferfactor over a first portion of the plate and a second heat transferfactor over a second portion of the plate wherein the first and secondportions of the plate are spaced apart over the length of the channeland the first heat transfer factor differs from the second heat transferfactor. Means are provided for passing a reaction fluid through aplurality of the reaction flow channels defined by the plates along afirst flow path. Means are also provided for passing a heat exchangefluid through a plurality of the heat exchange flow channels defined bythe plates along a second flow path. The apparatus can also includemeans for contacting the reaction fluid with a catalyst.

The preferred control parameter of this invention that allows eachindividual reaction zone to operate at or near a desired temperatureprofile is a variation in the pitch angle of the corrugations. Heattransfer enhancement provided by corrugations in the thin platesincreases as the corrugations become transverse to the flow of the heatexchange fluid. For example, in the case of an endothermic reaction,arranging the corrugations in a more parallel fashion with respect tothe heat transfer fluid at the inlet of the reaction zone and thecorrugations in a more transverse fashion toward the outlet end of thereaction zone will provide less heat transfer from the heat transferfluid at the inlet side than at the outlet side of the reaction zone. Inthis manner, the increased heat transfer of the corrugations toward theoutlet of the reaction zone compensates for loss in temperature of theheat exchange fluid as it passes through the reaction zone. The pitchangle of the corrugations may also be varied to compensate for anyincreasing heat requirements necessitated by the stage of reactionwithin the reaction zone. In this manner the variation in corrugationpitch allows the single pass of heat transfer fluid to maintain adesired temperature profile despite any loss of heat transfer fluidtemperature as it passes through the reaction zone. In more complexarrangements, it may also be possible to alter the heat transfercoefficient along the length of the reaction zone by changing the depthof the corrugations. However, the simplest means for controlling thetemperature within the reaction zone is by varying the pitch angle ofthe corrugations from more parallel to more transverse with respect tothe heat exchange fluid flow.

Changes in heat transfer fluid temperature may be further offset byvarying the number of flow channels in different reaction sections of asingle plate exchanger reaction arrangement. For a given cross sectionalflow area, increasing the number of flow channels decreases the space orgap between plates, increases the number of plates and increases heattransfer. By increasing the number of flow channels, the plate exchangesurface area is increased relative to other reaction sections to achievea more complete approach to the maximum temperature of the heat transferfluid. Application of the flow channel variation to an endothermicreaction would pass the heating fluid into a reactor and into a firstreaction section having plates defining a first number of flow channels.For the purposes of this description a reaction section refers to anarrangement of plates defining a fixed number of spaces between theplates. The heating fluid would then flow out of a first reactionsection into a redistribution manifold and then into a second reactionsection having a greater number of plates that define an increasednumber of flow channels for the heating fluid and for the reactants. Insuch an arrangement, the combination of pitch angle variations in thecorrugations of each reaction section would maintain the desiredtemperature profile within each reaction section and the increase in thenumber of plates or flow channels will maintain overall averagetemperatures from reaction section to reaction section within a singlesystem of reaction sections. Both of these effects will allowtemperature conditions within a process to be beneficially controlled.

Accordingly, in a process embodiment, this invention is a process forcontrolling the temperature of a reactant stream in a chemical reactionby indirect heat exchange with a heat exchange fluid across amultiplicity of plate elements. The process passes a heat exchange fluidfrom a heat exchange inlet to a heat exchange outlet through a first setof elongated channels formed by a first side of the plates. The processalso passes a reactant stream from a reactant inlet to a reactant outletthrough a second set of channels formed by a second side of the plates.The reactant stream may contact a catalyst in the second set ofchannels. The process exchanges heat between the heat exchange fluid andthe reactant stream by contacting at least the reactant or the heatexchange fluid with a first portion of the plates having a first heattransfer factor and a second portion of the plates having a second heattransfer factor wherein the first portion is spaced apart from thesecond portion and the first heat transfer factor is different from thesecond heat transfer factor.

The process may be useful in a wide variety of catalytic reactions. Thisinvention is most beneficially applied to catalytic conversion processhaving high heats of reaction. Typical reactions of this type arehydrocarbon conversion reactions that include: the aromatization ofhydrocarbons, the reforming of hydrocarbons, the dehydrogenation ofhydrocarbons, and the alkylation of hydrocarbons. Specific hydrocarbonconversion processes to which this invention are suited include:catalytic dehydrogenation of paraffins, reforming of naphtha feedstreams, aromatization of light hydrocarbons and the alkylation ofaromatic hydrocarbons.

The reaction zones for the process of this invention may indirectlycontact the reactants with the heat exchange fluid in any relativedirection. Thus, the flow channels and inlet and outlets of the reactionzones may be designed for cocurrent, countercurrent, or cross-flow ofreactant and heat exchange fluid. Preferred process arrangements forpracticing this invention will pass reactants in cross-flow to the heatexchange fluid. Cross-flow of reactants is generally preferred tominimize the pressure drop associated with the flow of reactants throughthe reactor. For this reason, a cross-flow arrangement can be used toprovide the reactants with a shorter flow path across the reaction zone.

The shorter flow path, particularly in the case of the reactant streamcontacting heterogeneous catalysts, reduces overall pressure drop of thereactants as they pass through the reactor. Lower pressure drops canhave a two-fold advantage in the processing of many reactant streams.Increased flow resistance i.e., pressure drop, can raise the overalloperating pressure of a process. In many cases, product yield orselectivity is favored by lower operating pressure so that minimizingpressure drop will also provide a greater yield of desired products. Inaddition, higher pressure drop raises the overall utility and cost ofoperating a process.

It is also not necessary to the practice of this invention that eachreactant channel be alternated with a heat exchange channel. Possibleconfigurations of the reaction section may place two or more heatexchange channels between each reactant channel to reduce the pressuredrop on the heat exchange medium side. When used for this purpose, aplate separating adjacent heat exchange channels may containperforations.

Additional embodiments, arrangements, and details of the invention aredisclosed in the following detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a catalytic reaction section ofthis invention showing a preferred direction for the circulation offluids and catalyst.

FIG. 2 is a schematic front view of a plate that forms a portion of thechannels in the catalytic reaction section of this invention.

FIG. 3 is a schematic exploded view of a catalytic reactor arranged inaccordance with this invention.

FIG. 4 is a sectional view taken at section 4--4 of FIG. 3.

FIG. 5 is a diagrammatic perspective view of a catalytic reactor of thisinvention with a star shaped arrangement of reactor stacks.

FIG. 6 is a transverse section view of the reactor arrangementrepresented in FIG. 5.

FIG. 7 is a transverse section view of an alternate interior arrangementfor the reactor of FIG. 5.

FIG. 8 is a diagrammatic elevation view of a typical catalytic reactionstack forming the star shaped arrangement of FIG. 5.

FIG. 9 is a sectional view along the line 6--6 of FIG. 8.

FIG. 10 is a diagrammatic perspective view of a catalytic reactor ofthis invention with a polygonally shaped arrangement of reactor stacks.

FIG. 11 is a section view along the line 11--11 of FIG. 10.

FIG. 12 is a section view along the line 12--12 of FIG. 10.

FIG. 13 is a partial diagrammatic elevation view of an alternatereaction stack arrangement according to this invention.

FIG. 14 is a section view along the line 14--14 of FIG. 13.

FIG. 15 is a transverse section view of another polygonal reactorarrangement according to the invention.

FIG. 16 is a process flow diagram of a dehydrogenation process accordingto the invention.

DETAILED DESCRIPTION OF THE INVENTION

By its very design, the reactor according to this invention has theadvantage of maintaining, with simple means, desired temperatureprofiles including isothermal or reverse gradient temperature conditionsduring the flow of the reactive fluid in the reactor, by means of a heattransfer medium.

The process and reactor arrangement may use homogeneous or heterogeneouscatalysts. Homogeneous catalyst will typically comprise liquid catalyststhat flow through reaction channels along with the reactants and areseparated for recovery and recycle outside of the reaction zone. Thisreactor arrangement provides particular benefits with heterogeneouscatalysts that are typically retained within the reactant channels bythe plates and permeable members that retain the catalyst but permit theflow of reactants therethrough. In most cases, the heterogeneouscatalyst will comprise particulate material retained between the platesand the reactor may be arranged to permit the continuous addition andwithdrawal of particulate material while the reactor is on stream.

The type and details of the reactor arrangements contemplated in thepractice of this invention is best appreciated by a reference to thedrawings. FIG. 1 is a schematic representation of a catalytic reactorsection designed to effect a catalytic reaction on a reactant fluidwhile using indirect heat exchange with a heat transfer fluid tomaintain favorable reaction temperatures as the reactant fluid flowsthrough the reaction section. To this end, the catalytic reactionsection comprises a stack of parallel plates 10 of the type representedin FIG. 2. Preferably each plate 10 has a central part 12 that formsinclined corrugations 13. Preferably each plate 10 will also containsmooth edges 11 that facilitate the assembly of multiple plates intochannels. Referring again to FIG. 1, each plate 10 is stacked next toadjacent plates 10 to form two circulation systems, the first one A fora flow of a reactive fluid and the second one B for flow of an auxiliaryfluid. Together FIGS. 1 and 2 define specific circulation systems A andB, wherein the reactive fluid and the heat exchange fluid respectively,flow in crosswise directions, i.e. perpendicular and through alternatechannels formed between adjacent plates 10.

Suitable plates for this invention will comprise any plates allowing ahigh heat transfer rate and which are readily formed into a pattern thatpermits variations in the heat transfer factor or that can retain meansfor varying the heat transfer factor. The plates may be formed intocurves or other configurations, but flat plates are generally preferredfor stacking purposes. Thin plates are preferred and typically have athickness of from 1 to 2 mm. The plates are typically composed ferrousor non-ferrous alloys such as stainless steels.

Referring again to FIG. 2 variation in the corrugation arrangement is apreferred method for controlling the temperature profile. The platearrangement for FIG. 2 represents a typical corrugation pattern for anexothermic or endothermic process. In order to maintain a substantiallyisothermal or rising temperature profile in such a preferred arrangementthe heat transfer fluid flows downwardly through the corrugations on oneside of the plate and the reactant stream flows horizontally across theplate on an opposite side. At the upper inlet end the pitch angle of thecorrugations is small, i.e. the principle direction of the corrugationsapproach a parallel alignment with the heat exchange fluid flow. At thelower end of the plate where the heat exchange fluid exits, the pitchangle of the corrugations is wide to increase relative heat transfer,i.e. the principle direction of the corrugations approach aperpendicular or transverse alignment with respect to the heat exchangefluid flow. Corrugation pitch angles can be in a range of from greaterthan 0° to less than 90° degrees. Typically the corrugation pitch anglefrom an inlet to an outlet section of a plate will range from about 10°to 80°, and more typically in a range of about 15° to 60°. In aparticularly preferred arrangement, the plates will make an angle ofless than 30° at the inlet end of the plate and an angle of more than35° at the outlet end of the plate. The varying corrugations may beformed in a continuous plate section or the plate section of the typeshown in FIG. 2 may be made from several plates having corrugations atdifferent pitch angles.

The plates may be spaced apart or positioned against adjacent plates toform the alternate flow channels. Narrow spacing between the plates ispreferred to maximize heat transfer surface. When using corrugations thecorrugation pattern will preferably be reversed between adjacent platesin a reactor section. In this manner the general herring bone pattern onthe faces of opposing corrugated plates will extend in oppositedirections and the opposing plate faces may be placed in contact witheach other to form the flow channels and provide structural support tothe plate sections.

Preferably system A, in which the reactant fluid circulates, includes aheterogenous catalyst in the form of particles. The catalyst particlestypically comprise grains of a small size. The particles may take on anykind of shape, but usually comprise small spheres or cylinders.

In addition, for the purpose of catalyst loading and unloading, thecatalytic reactor may include means for passing catalyst through thereactant channels. FIG. 1 shows such means 31, schematicallyrepresented, for distributing catalyst in the channels of system A, andin its lower part, means 32, schematically represented, for collectingcatalyst during replacement operations.

FIGS. 3 and 4 represent a highly schematic reactor arrangement of theinvention showing a generalized arrangement of plates assembled intoalternate channels. (In order to simplify the drawing the corrugationshave not been shown.) For this purpose, spacers 14 are attached, asrepresented in FIG. 3, by a suitable method such as welding along thesides of plates 10 to form channels 20, which are open along oppositevertical sides the reactor arrangement for the flow of reactant fluid asshown by arrows A (system A), and channels 30, which are open at the topand bottom of the reactor arrangement for the flow of heat exchangefluid as shown by the arrows B (system B).

When flowing through particle containing channels 20 of system A, thereactant fluid undergoes a catalytic reaction accompanied by aliberation or an absorption of heat. The function of the heat exchangefluid circulating in system B is to convey the heat to be added to orremoved from the reactive fluid, in order to maintain favorable reactionconditions. Such conditions can again include isothermal conditionsduring the circulation of the afore-mentioned reactive fluid in thecatalytic reactor or a reverse temperature gradient. The heat exchangefluid is either a gas or a liquid, depending on the specific operatingconditions of each process.

The specific heat transfer relationship for the plate exchange isestablished by the fundamental equation expressing heat transfer betweentwo fluids. This relationship is as follows:

    P=h×S×LMTD

where:

P is the amount of heat exchanged, h is the local or overall heattransfer coefficient, S is the heat exchange area between fluids, andLMTD is the logarithmic mean temperature difference.

The logarithmic mean temperature difference is readily determined by thedesired temperature difference at any point along the plate.

An essential element of this invention is a variation in the coefficientof thermal conductivity along the length of plates that define thereactant and heat exchange flow channels. For the purposes of thisinvention of the heat transfer factor is defined as the product of theheat transfer coefficient, h and the local heat exchange area S.Accordingly the heat transfer factor is defined as follows:

    K=h×S

The value of K that is important to this invention is its localizedvalue over different portions of the heat exchange plates. Variations inthe localized value of K over different portions of the plates may beachieved in a number of ways.

In addition to the use of corrugations as previously described, a nonuniform coating may be applied over the surface of the plates to cause avariation in the heat transfer coefficient at localized areas of theplates. In this manner the variations in the heat transfer coefficientare arranged to provide the necessary variations in K for a desiredtemperature profile. Suitable coatings that may be applied include lowinsulating value coatings and heat transferring enhancing coatings thatare well known to those skilled in the art. Where a phase change bringsabout boiling of heat exchange or reactant fluid such coatings caninclude nucleate boiling surfaces.

Another method of varying K is by inducing changes in thecharacteristics of the flow of the heat transfer fluid. Surfacevariations in the plates that break up any laminar boundary layer todifferent degrees along different portion of the plates will inducechanges in the heat transfer coefficient. The use insert plates withinthe channels as described in U.S. Pat. No. 5,540,899 is another methodof non-uniformly varying the flow regime to locally change K. Variationin the surface of the plates can also increase or decrease the effectiveheat transfer surface thereby inducing changes in K by changes in thesurface area as well as the heat transfer coefficient. Changes in thesurface area and heat transfer coefficient may be achieved by making thechannels wider or narrower. Methods of calculating K for sucharrangements are well known to those skilled in the art.

Considering then the preferred arrangement of this invention where aseries of corrugated plates define alternate channels of catalystparticles and heat exchanger fluid, the local or overall heat transfercoefficient can be calculated by using the following equation:

    h=f(a,e,dp)

where a is the pitch angle of the corrugations, e is the distancebetween two plates 10, and dp is the equivalent diameter of catalystparticles.

Appropriate values of h can be established by modeling or computed usingknown correlations for establishing heat transfer coefficients overcorrugated surfaces and, where present, through particle beds.Correlations for localized heat transfer through particle beds may befound in Leva, Ind. Eng. Chem., 42, 2498 (1950). Correlations for heattransfer along corrugations are presented in AIChE Symposium Series No.295 Vol. 89 Heat Transfer Atlanta (1993).

The area of exchange between the reactive fluid and the auxiliary fluidcan be calculated by using the equation:

    S=ε×n×1×L

where: ε is a correction factor for the elongation of the platesresulting from the corrugations, n is the number of plates in contactwith both heating and reactant fluids, 1 is the plate width, and L isthe plate length.

By varying the number of plates and the characteristics of thecorrugations, especially the pitch angle of the corrugations, theinvention provides means for maintaining desired temperature conditionsin the reactant fluid flow direction.

As shown in the embodiment of FIG. 3, the means for controlling andmaintaining temperature conditions consists of having distinct sections1a, 1b, 1c, 2a . . . 4b, 4c of heat exchange between the reactant fluidcirculating in system A and the heat exchange fluid circulating insystem B. In FIG. 3, the distinct heat exchange sections 1a, 1b, 1c, 2a. . . 4b, 4c are distributed in the reactant fluid flow direction and inthe heat exchange fluid flow direction, so as to form rows 1, 2, 3, and4, and columns a, b, and c. In other arrangements of this invention,these distinct heat exchange sections can be distributed solely in thereactant fluid flow direction or solely in the heat exchange fluid flowdirection. The total number of distinct reaction sections defined in theentire catalytic reactor of FIG. 3 is obtained by multiplying the numberof rows 1, 2, 3 and 4 by the number of columns a, b and c. All the heatexchange sections of a particular row have the same vertical height andall the heat exchange sections of a particular column have the samehorizontal width.

Varying the number of plates 10 as represented in FIGS. 3 and 4increases the heat exchange in the higher numbered rows or loweredlettered columns by adding heat exchange areas between the reactantfluid and the heat exchange fluid in each of the afore-mentionedsections. To obtain a variation of heat exchange within sections 1a, 1b,1c, 2a, 2b . . . 4b, 4c, this invention modifies each of these sectionsby preferably varying the pitch angle of the corrugations. Asrepresented in FIG. 2, the pitch angle of the corrugations 13 can bemore parallel in relation to the reactant fluid flow direction where ahigh transfer coefficient is required, and more transverse to the fluidflow direction in the heat exchange areas where a low transfercoefficient is required.

The number of plates 10 can increase or decrease from the entry to theexit of the reactive fluid. FIG. 4 shows, as an example, a variation ofheat exchange sections from a large number to a small number of plates10 along the flow path of the reactive fluid.

Where the invention uses a heterogeneous catalyst, the catalytic reactorincludes means for containing catalyst 15 in the channels 20 of thereactive fluid circulation system A. As shown in FIGS. 3 and 4, thecatalyst containing means can consist of grids 16 placed on either sideof channels 20 in each heat exchange area 1a, 1b, 1c, 2a . . . 4b, 4c.These grids 16 cover the whole width of channels 20, and the mesh sizeof each grid is inferior to the catalyst 15 grain size.

In addition, where the catalytic reactor of this invention uses amultiplicity of distinct heat exchange sections (1a, 1b, 1c, 2a . . .4b, 4c), means for mixing and distributing the reactive and/or the heatexchange fluid are provided. As shown in FIG. 4, these means consist ofconnecting distribution spaces 21 located between the afore-mentionedheat exchange areas.

FIGS. 5 and 6 diagrammatically show a more specific embodiment of acomplete reactor arranged according to this invention. The reactorcontains multiple reaction stacks with each stack containing multiplereaction sections. The reactor effects catalytic reaction of ahorizontally flowing reactant fluid under controlled temperatureconditions, by indirect contact with a vertically flowing heat transferfluid while permitting movement of catalyst through the reaction stacks.

The reactor comprises a vessel, of circular cross section, designated inits entirety by the reference 31 and shown by the dot-dash lines in FIG.5. The vessel 31 includes a head 32, for example of hemispherical shape,on which emerges a nozzle 33 for supplying heat exchange fluid, and abottom head 34, for example of hemispherical shape, on which emerges anozzle 35 for outlet of the heat exchange fluid.

As shown in FIG. 6, the catalytic unit includes two concentric walls 31aand 31b which are arranged inside vessel 31 and between which walls arearranged reaction stacks 36. Reaction stacks 36 are vertical anddistributed in a star configuration between walls 31a and 31b of vessel31. FIG. 7 shows a variation of FIG. 6 wherein vessel 31 constitutesouter wall 31a. The number of reaction stacks 36 is preferably an evennumber and, in FIGS. 5-7, is equal to six.

The sides of reaction stacks 36 define a portion of feed zones 37a, 37cand 37e arranged alternately between stacks 36 for distributing thereactive fluid and a portion of recovery zones 37b, 37d and 37f arrangedalternately between stacks for recovering the reactive fluid. Upperparts of the zones 37a, 37b . . . 37f are blocked off by horizontalplates 38, each arranged between the reaction stacks 36, and the lowerparts of the zones 37a, 37b . . . 37f are blocked off by horizontalplates 39, each arranged between the reaction stacks 36. The stararrangement gives each zone 37a, 37b . . . 37f a triangular prismaticshape, with one of the apexes oriented towards the inside of the vessel36. In other embodiments, not shown, each zone 37a . . . 37f may bedivided by a vertical wall into two half-zones with the subdivided partsof the zones providing one feed zone and one recovery zone.

The feed zones 37a, 37c, and 37e are joined to means for inlet of thereaction fluid, which in one form comprises pipes 42, and the recoveryzones 37b, 37d and 37f are joined to means for discharging this reactionfluid which in one form comprise pipes 41.

As shown in FIGS. 8 and 9, each reaction stack 36 comprises a pluralityof parallel plates 40. The plates 40 are arranged perpendicular to theradius of the vessel 31 and extend downwardly through each of thereaction stacks 36. Each plate 40 forms, together with the adjacentplates 40, the previously described circulation circuits A and B.Channels 43 contain horizontal flow through circuit A for the passage ofthe reactant fluid and channels 44 contain vertical flow through circuitB for the passage of the heat transfer fluid. The circuit A forcirculation of the reactive fluid again contains a particulate catalyst45. The reactor contains means for passing catalyst into the circuit Aof each reaction stack 36 and means for withdrawing catalyst from thecircuit A of each reaction stack 36. As shown in the specificarrangement of FIG. 5, catalyst feed pipes 46, the number of which isequal to half the number of reaction stacks 36, receive fresh catalystparticles. Each pipe 46 is divided into two sub-pipes 46a and 46b, thatdeliver catalyst particles to the upper part of reaction stack 20.

A plurality of catalyst discharge pipes 47 are each connected with alower part of each reaction stack 36. Pipes 47 pass directly out ofvessel 31 to improve catalyst removal. Catalyst particles may be removedfrom the reactor either periodically or continuously and returned to thereactor stacks after regeneration.

FIGS. 5 and 8 show a diffuser 48 in the upper part of each reactionstack for distributing catalyst into circuit A and a collector 50 at thebottom of stacks 36 for withdrawing catalyst. Diffusers 48 may be fittedwith internal baffles or corrugations 13 for distributing the catalyst.Each collector 50 includes internal baffles or corrugations 51 toregulate the flow of catalyst into pipe 47.

Each reaction stack 36 includes, in its upper part, at least one inletfor receiving the heat exchange fluid into circuit B. The inlet may be asingle opening. FIGS. 5 and 8 show reaction stack 36 having the inlet inthe form of two lateral bowl shaped inlets 52 each arranged on oppositesides of the corresponding reaction stack 36. Inlet 52 opens to theinterior of vessel 31, which contains the heat exchange fluid from fluidnozzle 33. The heat exchange fluid is introduced into circuit B frominlet 52 by a distribution zone 52a.

Each reaction stack 36 also typically includes, in its lower part, atleast one collector for recovering the heat exchange fluid at the outletof the circuit B. FIGS. 5 and 8 show each reaction stack 36 having twolateral collectors 53, each arranged on one side of the reaction stack36 to receive heat transfer fluid from a recovery zone 53a thatcommunicates with channels 44. The collectors communicate, via the openportion of the vessel 31 below plate 39, with the outlet nozzle 35 forwithdrawing the heat exchange fluid.

The embodiment shown in FIGS. 5-9 shows each reaction stack 36 dividedinto a plurality of reaction sections 36a, 36b, 36c and 36d which arejoined together by intermediate connecting zones 54. Connecting zones 30serve as redistribution manifolds to permit the segregated passage ofthe heat exchange fluid and the catalyst between the various reactionsections 36a, 36b, 36c and 36d.

A typical mode of operation passes reactant fluid, heat exchange fluidand, optionally, catalyst through the reactor 31. Reactant fluid entersreactor 31 via the pipes 42, passes into the feed zones 37a, 37c and37e, then passes horizontally through two adjacent reaction stacks 36via the circuit A and emerges in the recovery zones 37b, 37d and 37f.Pipes 41 subsequently discharge the reactant fluid. The heat exchangefluid enters the upper part of the vessel 31 via the nozzle 33, passesinto the reactor stacks 36 via the inlet zones 52 and the distributionzone 52a. The heat exchange fluid passes vertically through the reactorstacks 36 via the circuit B and exits the reaction stack 36 via therecovery zones 53a and the collectors 53. The heat exchange fluidemerges into the lower part of the vessel 31 and exits via the nozzle35. Catalyst 45 enters circuit A of each reaction stack 36 via the pipes46, the sub-pipes 46a and 46b and the diffuser 48 wherein the reactivefluid contacts the catalyst in the circuit A. Collectors 50 and pipes 47periodically or continuously withdraw catalyst from the bottom ofreaction stack 36.

In order to maintain the desired temperature profiles while the reactantfluid passes through the catalyst of each reaction section 36a, 36b, 36cand 36d, each section varies the pitch angle of the corrugations definedby plates 40. The number of plates in each successive downwardly locatedreaction section 36(a-d) increases to progressively add surface area forheat exchange between the reaction fluid and the heat exchange fluiddown the length of each reaction stack 36.

Preferably, the reaction stacks 36 are kept under compression withinvessel 31 by the heat exchange fluid. The operating pressure of the heatexchange fluid is typically regulated to a value slightly higher thanthat of the reaction fluid. For this purpose, the heat exchange fluidusually fills the vessel 31 and surrounds the reaction stacks 36.

The vessel 31, may have the reaction stacks 36 located therein in avariety of different arrangements. Another type of arrangement as shownin FIG. 10 places the reaction stacks such that the plates 40 aresubstantially parallel to the radius of a vessel 55. The arrangements ofplates 40 parallel to the radius of vessel 55 provides a generallypolygonal configuration for the reaction stacks. The reaction stacksform a substantially circumferential ring within the reactor vessel 55.

In FIGS. 10-12, piping and duct arrangements for the delivery andrecovery of reaction fluids, heat exchange fluids, and catalysts aresubstantially similar to those described for the reactor arrangement ofFIGS. 5-9 and all details of the reaction stacks are also substantiallysimilar to those described. Catalyst particles enter the reactor vessel10 through nozzle 56. Diffusers 48' at the top of reaction stacks 36'transfer the catalyst into the reaction stacks across upper head 58.Nozzles 57 withdraw catalyst from the reactor stacks 36' through acollector of the type previously described and across lower head 59. Theheat exchange fluid enters reactor 55 through a nozzle and fills theinterior of vessel 55. The heat transfer fluid enters the reactionstacks 36' through an inlet 52' and passes through adjoining reactionsections by connecting zones 54'. Collectors at the bottom of reactorstacks 36' discharge the heat exchange fluid into a collection manifold61. Pipes 62 withdraw heat exchange fluid from manifold 61. Pipes 63collects heat exchange fluid from pipes 62 to withdraw the heat exchangefluid from vessel 55. Additional details of manifold 61 and pipes 62 and63 are shown in FIG. 12. The reaction fluid flows through vessel 55 froman inlet nozzle 64 to an outlet nozzle 65. Nozzle 64 distributes thereaction fluid to multiple distributor pipes 66. Each distributor pipe66 delivers reaction fluid to a distribution chamber 67. Eachdistribution chamber 67 covers the side of each reaction stack 36' thatfaces the interior of the vessel 55. Distribution chambers 67 have aclosed bottom that forces the flow of reaction fluid across eachreaction stack 36' and into a collector 68 that seals an opposite faceof each reaction stack 36'. The upper portion of each collector 68 isclosed to direct the exiting flow of reaction fluid into conduits 69 forcollection and withdrawal by nozzle 65.

In another embodiment shown in FIGS. 13 and 14, the reactor stacks 36'are connected into a substantially polygon shape and housed by reactorvessel 55. Plates 70 shown in FIG. 14 define an inner distribution space71 for the reaction fluid. As shown in FIG. 13, an upper baffle 72 and alower baffle 73 form the upper and lower boundaries of distributionspace 71. The reaction fluid enters the distribution space across upperbaffle 72 via nozzle 64 and flows from inner distribution space 71 intoan outer collection space 74. Outer collection space 74 eliminates thenecessity for collection piping and the reaction fluid exits the vesseldirectly from an open nozzle 65 (not shown). Unlike the previous reactorconfigurations, the embodiment of FIGS. 13 and 14 shows the reactionfluid surrounding the reaction stacks 36'. A baffle 35, together withbaffle 33 isolates the upper portion of vessel 55 to form a distributionchamber for delivery of the heat exchange fluid into inlets 52' in themanner previously described. The heat exchange fluid again exits thereactions stacks 36' through a manifold and piping system tosubstantially the same as that shown in FIGS. 10-12. Any flow ofcatalyst practiced in the embodiment of FIGS. 13 and 14 occurs inessentially the same manner as that previously described.

FIG. 15 shows an arrangement for reaction stacks 35' that combines theinlet distribution space of FIGS. 13 and 14 with the collection bafflesshown in FIGS. 10-12. In the arrangement shown in FIG. 15, any catalystflow again occurs in the same manner as that previously described. Inregard to reaction fluid, it flows into central chamber 71 in the mannerassociated with FIGS. 13-14 and is collected and withdrawn from thereaction stacks 36' in the manner associated with FIGS. 10-12. With thearrangement of reaction stacks as shown in FIG. 15, the flow of heatexchange fluid through the reactor may be controlled with two differentpiping and baffling arrangements. The entering heat exchange fluid maysurround the reaction stacks 36' and fill the interior of vessel 55while a manifold system similar to that depicted in FIGS. 10-12withdraws the effluent heat exchange fluid. In another arrangement,baffles such as those depicted in FIGS. 13 and 14 seal off an uppervolume of vessel 55 to distribute incoming heat exchange fluid to inlets52' while the effluent heat exchange fluid surrounds reaction stacks 36'and is withdrawn from the open lower volume without the use of anymanifold or piping system.

Catalytic reforming is a well established hydrocarbon conversion processemployed in the petroleum refining industry for improving the octanequality of hydrocarbon feedstocks, the primary product of reformingbeing motor gasoline. The art of catalytic reforming is well known anddoes not require extensive description herein. Briefly, in catalyticreforming, a feedstock is admixed with a recycle stream comprisinghydrogen and contacted with catalyst in a reaction zone. The usualfeedstock for catalytic reforming is a petroleum fraction known asnaphtha and having an initial boiling point of about 180° F. (80° C.)and an end boiling point of about 400° F. (205° C.). The catalyticreforming process is particularly applicable to the treatment ofstraight run gasoline comprised of relatively large concentrations ofnaphthenic and substantially straight chain paraffinic hydrocarbons,which are subject to aromatization through dehydrogenation and/orcyclization reactions. Reforming may be defined as the total effectproduced by dehydrogenation of cyclohexanes and dehydroisomerization ofalkylcyclopentanes to yield aromatics, dehydrogenation of paraffins toyield olefins, dehydrocyclization of paraffins and olefins to yieldaromatics, isomerization of n-paraffins, isomerization ofalkylcycloparaffins to yield cyclohexanes, isomerization of substitutedaromatics, and hydrocracking of paraffins. Further information onreforming processes may be found in, for example, U.S. Pat. Nos.4,119,526 (Peters et al.); 4,409,095 (Peters); and 4,440,626 (Winter etal), the contents of which are herein incorporated by reference.

A catalytic reforming reaction is normally effected in the presence ofcatalyst particles comprised of one or more Group VIII noble metals(e.g., platinum, iridium, rhodium, palladium) and a halogen combinedwith a porous carrier, such as a refractory inorganic oxide. The halogenis normally chlorine. Alumina is a commonly used carrier. The preferredalumina materials are known as the gamma, eta and the theta alumina withgamma and eta alumina giving the best results. An important propertyrelated to the performance of the catalyst is the surface area of thecarrier. Preferably, the carrier will have a surface area of from 100 toabout 500 m² /g. The particles are usually spheroidal and have adiameter of from about 1/16th to about 1/8th inch (1.5-3.1 mm), thoughthey may be as large as 1/4th inch (6.35 mm). A preferred catalystparticle diameter is 1/16th inch (3.1 mm). During the course of areforming reaction, catalyst particles become deactivated as a result ofmechanisms such as the deposition of coke on the particles; that is,after a period of time in use, the ability of catalyst particles topromote reforming reactions decreases to the point that the catalyst isno longer useful. The catalyst must be reconditioned, or regenerated,before it can be reused in a reforming process.

In preferred form, the reforming operation will employ a moving bedreaction zone and regeneration zone. The present invention is applicableto moving bed and fixed bed zones. In a moving bed operation, freshcatalyst particles are fed to a reaction zone by gravity. Catalyst iswithdrawn from the bottom of the reaction zone and transported to aregeneration zone where a multi-step regeneration process is used torecondition the catalyst to restore its full reaction promoting ability.Catalyst flows by gravity through the various regeneration steps andthen is withdrawn from the regeneration zone and furnished to thereaction zone. Movement of catalyst through the zones is often referredto as continuous though, in practice, it is semi-continuous. Bysemi-continuous movement is meant the repeated transfer of relativelysmall amounts of catalyst at closely spaced points in time. A moving bedsystem has the advantage of maintaining production while the catalyst isremoved or replaced.

Another preferred hydrocarbon conversion process is the alkylation ofaromatic hydrocarbons. In aromatic alkylation suitable aromatic feedhydrocarbons for this invention include various aromatic substrates.Such substrates can be benzene or alkylated aromatic hydrocarbons suchas toluene. The acyclic feed hydrocarbon or alkylating agent that may beused in the alkylation reaction zone also encompasses a broad range ofhydrocarbons. Suitable alkylating agents include monoolefins, diolefins,polyolefins, acetylenic hydrocarbons and other substituted hydrocarbonsbut are preferably C₂ -C₄ hydrocarbons. In the most preferred form ofthis invention, the alkylation agent will comprise C₂ -C₄ monoolefins.

A wide variety of catalysts can be used in the alkylation reaction zone.The preferred catalyst for use in this invention is a zeolite catalyst.The catalyst of this invention will usually be used in combination witha refractory inorganic oxide binder. Preferred binders are alumina orsilica. Preferred alkylation catalysts are a type Y zeolite having analumina or silica binder or a beta zeolite having an alumina or silicabinder. The zeolite will be present in an amount of at least 50 wt. % ofthe catalyst and more preferably in an amount of at least 70 wt. % ofthe catalyst.

The alkylation reaction zone can operate under a broad range ofoperating conditions. Temperatures usually range from 100° C. to 325° C.with the range of about 150°-275° C. being preferred. Pressures can alsovary within a wide range of about 1 atmosphere to 130 atmospheres. Sinceliquid phase conditions are generally preferred within the reactionzone, the pressure should be sufficient to maintain the reactants insuch phase and will typically fall in a range of from 10 to 50atmospheres. Reactants generally pass through the alkylation zone at amass flow rate sufficient to yield a liquid hourly space velocity from0.5 to 50 hrs⁻¹ and especially from about 1 to 10 hrs⁻¹.

The alkylation zone is ordinarily operated to obtain an essentiallycomplete conversion of the alkylating agent to monoalkylate andpolyalkylate. To achieve this effect, additional aromatic substrate willusually be charged to the reaction zone. Thus, the feed mixtures areintroduced into the reaction zone at a constant rate and a molecularratio of about 1:1 to 20:1 aromatic substrate to alkylating agent with aration of about 2:1 to 10:1 being preferred. As a result, in addition toproduct there will usually be a substantial amount of unreacted aromaticsubstrate that is removed with the product stream from the alkylationreaction zone. Additional details of aromatic alkylation processes canbe found in U.S. Pat. No. 5,177,285, the contents of which are herebyincorporated by reference.

Catalytic dehydrogenation is another example of an endothermic processthat advantageously uses the process and apparatus of this invention.Briefly, in catalytic dehydrogenation, a feedstock is admixed with arecycle stream comprising hydrogen and contacted with catalyst in areaction zone. Feedstocks for catalytic dehydrogenation are typicallypetroleum fractions comprising paraffins having from about 3 to about 18carbon atoms. Particular feedstocks will usually contain light or heavyparaffins. For example a usual feedstock for producing a heavydehydrogenation products will comprise paraffins having 10 or morecarbon atoms. The catalytic dehydrogenation process is particularlyapplicable to the treatment of hydrocarbon feedstocks containingsubstantially paraffinic hydrocarbons which are subject todehydrogenation reactions to thereby form olefinic hydrocarboncompounds.

A catalytic dehydrogenation reaction is normally effected in thepresence of catalyst particles comprised of one or more Group VIII noblemetals (e.g., platinum, iridium, rhodium, palladium) combined with aporous carrier, such as a refractory inorganic oxide. Alumina is acommonly used carrier. The preferred alumina materials are known as thegamma, eta and theta alumina with gamma and eta alumina giving the bestresults. Preferably, the carrier will have a surface area of from 100 toabout 500 m² /g. The particles are usually spheroidal and have adiameter of from about 1/16th to about 1/₋₋ th inch (1.5-3.1 mm), thoughthey may be as large as 1/4th inch (6.35 mm). Generally, the catalystparticles have a chloride concentration of between 0.5 and 3 weightpercent. During the course of a dehydrogenation reaction, catalystparticles also become deactivated as a result of coke deposition andrequire regeneration, similar to that described in conjunction with thereforming process; therefore, in preferred form, the dehydrogenationprocess will again employ a moving bed reaction zone and regenerationzone.

Dehydrogenation conditions include a temperature of from about 400° toabout 900° C., a pressure of from about 0.01 to 10 atmospheres and aliquid hourly space velocity (LHSV) of from about 0.1 to 100 hr⁻¹.Generally, for normal paraffins, the lower the molecular weight thehigher the temperature required for comparable conversions. The pressurein the dehydrogenation zone is maintained as low as practicable,consistent with equipment limitations, to maximize the chemicalequilibrium advantages. The preferred dehydrogenation conditions of theprocess of this invention include a temperature of from about 400°-700°C., a pressure from about 0.1 to 5 atmospheres, and a liquid hourlyspace velocity of from about 0.1 to 100 hr⁻¹.

The effluent stream from the dehydrogenation zone generally will containunconverted dehydrogenatable hydrocarbons, hydrogen and the products ofdehydrogenation reactions. This effluent stream is typically cooled andpassed to a hydrogen separation zone to separate a hydrogen-rich vaporphase from a hydrocarbon-rich liquid phase. Generally, thehydrocarbon-rich liquid phase is further separated by means of either asuitable selective adsorbent, a selective solvent, a selective reactionor reactions or by means of a suitable fractionation scheme. Unconverteddehydrogenatable hydrocarbons are recovered and may be recycled to thedehydrogenation zone. Products of the dehydrogenation reactions arerecovered as final products or as intermediate products in thepreparation of other compounds.

The dehydrogenatable hydrocarbons may be admixed with a diluent gasbefore, while, or after being passed to the dehydrogenation zone. Thediluent material may be hydrogen, steam, methane, carbon dioxide,nitrogen, argon and the like or a mixture thereof. Hydrogen is thepreferred diluent. Ordinarily, when a diluent gas is utilized as thediluent, it is utilized in amounts sufficient to ensure a diluent gas tohydrocarbon mole ratio of about 0.1 to about 20, with best results beingobtained when the mole ratio range is about 0.5 to 10. The diluenthydrogen stream passed to the dehydrogenation zone will typically berecycled hydrogen separated from the effluent from the dehydrogenationzone in the hydrogen separation zone.

Water or a material which decomposes at dehydrogenation conditions toform water such as an alcohol, aldehyde, ether or ketone, for example,may be added to the dehydrogenation zone, either continuously orintermittently, in an amount to provide, calculated on the basis ofequivalent water, about 1 to about 20,000 weight ppm of the hydrocarbonfeed stream. About 1 to about 10,000 weight ppm of water addition givesbest results when dehydrogenating paraffins having from 6 to 30 morecarbon atoms. Additional information related to the operation ofdehydrogenation catalysts, operating conditions, and processarrangements can be found in U.S. Pat. Nos. 4,677,237; 4,880,764 and5,087,792, the contents of which are hereby incorporated by reference.

EXAMPLE

The effect of using the process and reactor arrangements of thisinvention to maintain isothermal conditions was investigated in ahydrocarbon conversion process for the dehydrogenation of paraffins. Asimulation based on the ability of this invention to maintain isothermalconditions was prepared based on a feedstream having a composition givenin Table 1. The isothermal conditions that result from this inventionwere simulated in a dehydrogenation process as depicted in FIG. 16.

In this process simulation, a feedstream carried via line 100 and havingthe composition given in Table 1 passes into a heater 101 that raisesthe feedstream temperature from approximately 600° F. to 850° F. At thesame time, a heat exchange medium having the same relative compositionas feedstream 100 is carried via line 102 into a heater 103. Heater 103raises the temperature of the heat exchange fluid to approximately 890°F.

A line 104 carries the heated feedstream into a reactor 105 that directsthe feedstream into a heat exchange bundle 106 designed in accordancewith this invention. Reactor 105 has an arrangement to pass thefeedstream through a circuit A containing a typical dehydrogenationcatalyst comprising platinum on an alumina support. A line 107 carriesthe heat exchange fluid from heater 103 into reactor 105 which passesthe heat exchange medium downwardly through the heat exchange bundle 106in the manner previously described in relation to circuit B. The processsimulation of reactor bundle 106 is based on the use of a heat exchangebundle 106 having three layers of catalyst, a vertical height of about1.5 m, and a width of about 100 mm. The plates defining the channelswhich alternate between catalyst and feedstream and the heat exchangefluid have a thickness of about 1.2 mm, corrugations with a depth ofabout 10 mm and a width of about 270 mm. The plates are placed next toeach other in an alternating pattern of corrugations, such that thepeaks of the corrugations are in contact. The reactor operates at anaverage pressure of about 20 psig in both circuits A and B. The totalpressure drop through the system for the reaction fluid is about 2 psi.Indirect heat exchange of the reaction fluid with the heat exchangemedium provides an outlet mean temperature of about 850° F.

The converted reactant stream and the heating stream are recovered fromthe process. The product stream 108 having the composition given in thetable is withdrawn from the reactor at a temperature of about 850° F. Aline 109 carries the heat exchange medium from the reactor at atemperature of about 870° F. A comparison of process streams 100 and 108shows the conversion of C₁₀ to C₁₄ paraffins to corresponding olefins.

                  TABLE 1                                                         ______________________________________                                        Stream Description lb mole/hr                                                                  100       102     108                                        ______________________________________                                        Molar Flow       14.7195   15.2562 86.4876                                    H.sub.2 O        0.2044    0.2044  1.3073                                     Hydrogen         11.0421   11.5787 70.6316                                    Methane          0.0725    0.0725  0.4637                                     Ethane           0.1411    0.1411  0.9027                                     Propane          0.0308    0.0308  0.1968                                     n-Butane         0.0093    0.0093  0.0592                                     n-Pentane        0.0026    0.0026  0.0165                                     n-Decane         0.3509    0.3023  1.4082                                     n-C11            1.4016    1.1810  5.6242                                     n-C12            1.0262    0.8454  4.1177                                     n-C13            0.4162    0.3340  1.6701                                     n-C14            0.0207    0.0161  0.0829                                     1-Nonene         0.0000    0.0001  0.0000                                     1-Decene         0.0000    0.0486  0.0000                                     1-Undecene       0.0000    0.2206  0.0000                                     1-Dodecene       0.0000    0.1807  0.0000                                     1-Tridecene      0.0000    0.0822  0.0000                                     Total:           14.7195   15.256  86.4876                                    ______________________________________                                    

What is claimed is:
 1. A reactor for controlling temperature profiles ina reaction zone, said reactor comprising:a plurality of spaced apartplates with each plate having an extended length and defining a boundaryof a continuous heat exchange flow channel on one side of said plate anda boundary of a continuous reaction flow channel on an opposite side ofsaid plate and each plate defining a first heat transfer factor over afirst portion of said plate and a second heat transfer factor over asecond portion of said plate wherein said first and second portions ofsaid plate are spaced apart over the length of said channel and saidfirst heat transfer factor differs from said second heat transferfactor; means for passing a heat exchange fluid through a plurality ofsaid reaction flow channels defined by said plates along a first flowpath; and, means for passing a heat exchange fluid through a pluralityof said heat exchange flow channels defined by said plates along asecond flow path.
 2. The reactor of claim 1 wherein said first flow pathis perpendicular to said second flow path.
 3. The reactor of claim 1wherein said plates are discontinuous and said first portion comprises afirst plate section and said second portion comprises a second platesection.
 4. The reactor of claim 1 wherein said plates are continuousand define continuous corrugations over the length of said plates andthe pitch angle of said corrugations varies over the length of eachplate to vary said coefficients of thermal conductivity.
 5. The reactorof claim 4 wherein the pitch angle of said corrugations with respect tothe heat transfer fluid flow direction makes an angle of less than 30°at an inlet end of said plate and an angle of more than 35° at an outletend of said plate.
 6. The reactor of claim 1 wherein said reactorincludes means for retaining catalyst in said reaction flow channels. 7.The catalytic reactor of claim 1 wherein said plates are parallel. 8.The reactor of claim 1 wherein each of said plates in said reactordefines a reactant channel on one face and a heat exchange channel on anopposite face.
 9. The reactor of claim 1 wherein each heat exchangechannel is divided by a plate having an extended length.
 10. The reactorof claim 1 wherein the surface area of said first portion and saidsecond portion vary to alter the heat transfer factor.
 11. The reactorof claim 1 wherein the surface configuration of said first portionvaries with respect to said second portion to alter the heat transferfactor.
 12. The reactor of claim 1 wherein:said plurality of spacedapart plates comprises a first extended stack of plates located in areaction vessel; a second extended stack of plates comprising aplurality of spaced apart plates is located in said reaction vessel in alocation horizontally offset from said first extended stack of plates,with each plate in said second extended stack of plates having anextended length and defining a boundary of a continuous heat exchangeflow channel on one side of said plate and a boundary of a continuousreaction flow channel on an opposite side of said plate and each platedefining a first heat transfer factor over a first portion of said plateand a second heat transfer factor over a second portion of said platewherein said first and second portions of said plate are spaced apartover the length of said channel and said first heat transfer factordiffers from said second heat transfer factor; said means for passing areaction fluid passes said reaction fluid along a first flow paththrough a plurality of said reaction flow channels defined by saidplates in said second extended stack of plates; and, said means forpassing a heat exchange fluid passes a heat exchange fluid along asecond flow path through a plurality of said heat exchange flow channelsdefined by said plates in said extended stack of plates.
 13. The reactorof claim 12 wherein each of said extended stacks of plates comprise anupper reaction section and a lower reaction section located directlybelow said upper reaction section, said upper reaction section and saidlower reaction section contain a different number of plates and each ofsaid reaction stacks includes a connection duct for communicatingvertical flow channels between said upper and lower reaction sections.